When communicating data in communication networks, data is communicated between various communication network nodes on various communication links. Due to different reasons, a connection may be disturbed and fail, which is also the case for arrangements and devices in the communication network nodes.
A “Small Form factor Pluggable transceiver” (SFP) is an transforming component which is used in nodes in communication networks for connecting incoming cables and communication hardware in the communication network nodes, and converting between different media and coding representations. For instance, an SFP will be used for distribution of data between incoming optical fibres and electronic communication hardware and transforms the data between the different representations of the optical fibres and the communication hardware, i.e. between optical formatted data and electrical formatted data. For instance, such communication hardware could be data-plane hardware, or forwarding hardware, such as various network processors, switches or routing ASICs (Application Specific Integrated Circuit), which are applied in accordance with the OSI (Open Systems Interconnection) model on layer 2 and above.
An SFP comprises one or more optical inputs for connecting optical fibres, and one or more electrical outputs for connecting to the communication hardware. The optical inputs are arranged to receive an incoming optical cable, which may comprise one or more optical fibres. SFPs are manufactured for as well single mode fibres as multimode fibres. Typically, an optical cable comprises two optical fibres for transferring data in different directions. However, there are also Bi-Directional optical cables, which use one and the same optical fibre for data transferring in different directions.
Other types of SFPs are also available, as e.g. C-SFP (Compact SFP) which is able to simultaneously serve two data-plane ports, QSFP (Quad SFP) which is able to simultaneously serve four data-plane ports. Enhanced versions of SFPs are also available, as e.g. SFP+ and QSFP+ which are capable to be applied for higher bitrates, typically up to 10 Gbit/s
In another variant of SFP, both the first representation and the second representation are electrical but different from each other. Typically, the first electrical representation is then suitable for data transmission between communication network nodes and the second electrical representation is suitable for data transmission internally within a communication network node. In such SFPs the connected communication network nodes are connected by electrical cables.
In this description the term “data-plane” will be used to define a part of the architecture of an arrangement in a communication network node which is an interface to another communication network node with which the present communication node exchanges data, as well as connection between node internal data-planes. For instance, a data-plane connects a core network node with the present communication network node. In literature, the term forwarding plane is sometimes alternatively used instead of data-plane.
Transport of information from a radio base station (RBS) to a communication node has traditionally been performed on a single connection. However, if a connection will be cut-off or be seriously disturbed, an RBS will lose its communication with the communication node.
With reference to FIG. 1, a situation in a communication network will now be described.
A radio network controller (RNC) 100 is arranged to distribute data from a plurality of RBSs 104, 106 to a core network 108, where each RBS 104, 106 communicates data on a respective single connection (not referred to). Each one of the connections is connected to a line board 102 of the RNC 100 with a respective SFP to a data-plane ports (not shown), as seen in the figure. In case of communication failure for a connection or a defect SFP, the respective RBS 104, 106 loses its connection and will not be able to communicate with the core network 108 any longer.
One way to overcome the above described disadvantage is to provide redundancy to the connection, and a situation where redundancy is provided will now be described with reference to FIG. 2. A radio network controller (RNC) 200 is arranged to distribute data from a plurality of RBSs 204, 206 to a core network 208, where each RBS 204, 206 communicates data on a respective single connection (not referred to). Each one of the connections is connected to a line board 202 of the RNC 200 with a respective SFP to a respective data-plane port (not shown). The situation is similar to the situation described with reference to FIG. 1, but is completed with functionality for providing redundancy to the connection. As seen in the figure, each SFP is additionally connected to a further data-plane, and the RBSs are interconnected to each other by an interconnecting cable 210. Furthermore, are switches 212, 214 additionally arranged at the line board 202. In this situation, the SFP to which the first RBS 204 is connected is defect (indicated by a dashed cross in the figure), and the first RBS applies instead the interconnecting cable 210 to communicate with the RNC 200 via the second RBS 206. Thereby, by using data-plane ports of the other RBSs 204, 206, the RBSs 204 and 206 are able to communicate via respective active data-plane ports, and further with the core network 208.
When designing a communication system for providing communication between RBSs and the core network, there is a need to achieve a more robust redundant communication system.